Ultra Low Power Platform for Remote Health Monitoring

ABSTRACT

An apparatus and method is described to sense sparse signals from a medical device using compressed sensing and then transmitting the data for processing in the cloud.

PRIORITY CLAIM

This application claims the benefit under 35 USC 119(e) to U.S. Provisional Patent Application Ser. No. 61/852,967, filed on May 14, 2013 and titled “A compressed sensor platform for remote health monitoring,” and U.S. Provisional Patent Application Ser. No. 61/742,796, filed on Sep. 13, 2012 and titled “An ultra low power platform for Sparse Sensor Networks,” both of which are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to the field of sensor implementations. In particular, an apparatus and method is described to sense sparse signals from a medical device using compressed sensing and then transmitting the data for processing in the cloud.

BACKGROUND OF THE INVENTION

A typical prior art sensor network used for remote health monitoring is depicted in FIG. 1. The two main components are sensor block 200 and computing device 300, which here is an intelligent backend device. Sensor block 200 typically is a medical device for obtaining data from a patient, such as an electroencephalograph, cardiotocograph, or other device. Sensor block 200 comprises an amplifier (100), an analog-to-digital (ADC) conversion block 101, a post processor 102, a transmitter 103, and an antenna 104. It is to be understood that other sensor blocks similar to sensor block 200 can be used with the same computing device 300. For brevity's sake, only sensor block 200 is depicted in FIG. 1.

Computing device 300 may be a PC, server or any product with processing capabilities. Sensor block 200 obtains data from a patient, such as brain signals, heart signals, temperature, etc. using electrodes or other means, amplifies the sensed analog signals using amplifier 100, converts the analog signal into digital data using analog-to-digital conversion block 101, and processes the raw digital data using post processor 102, which can packetize the data, add headers, encrypt the data, and perform other known techniques. The packetized data is then send to computing device using transmitter 103 and antenna 104 over network 105. Network 105 can be a wireless network, a hardwired network, or a combination of the two.

The prior art sensor network of FIG. 1 has several drawbacks. First, sensor block 200 consumes a substantial amount of power. This is mainly because the sensor runs at full speed. As an example, if sensor block 200 is generating electroencephalography (EEG) signals, the signal bandwidth will include frequencies up to 1 KHz, and analog-to-digital converter 20 will need to perform sampling of the analog signal at a rate of at least 2 KHz (which is the Nyquist rate of the highest frequency in the signal). In addition, transmitter 103 will needs to transmit at that same rate, 2 KHz. In a typical medical device, transmitter 103 can consume 80% of the total power consumed by the device. For some applications where packetization and encryption needs are large, the post processing block may be the power bottleneck since it too runs at or above the Nyquist rate.

Second, computing device 300 needs to store all the data it receives and process it. Typically the computing device 300 will process the received data and take actions in response to the data (for example, begin an audio alarm). It can be appreciated that computing device 300 performs a substantial amount of data analysis and typically will generate a user interface that creates a visual display of the data obtained by sensor block 200. The large amount of data leads to high storage costs and consumes a significant amount of processing time and power.

Third, security is a major implementation drain. Sending data over wireless links requires some mode of encryption, all of which require extra power and resources.

What is needed is an improved sensor network that with sensor blocks that transmit less data and a computing device that operates on less data than in prior art sensor networks.

SUMMARY OF THE INVENTION

The aforementioned problem and needs are addressed through an embodiment that utilized compressed sensing within the sensor block. Compressed sensing can be used to process analog signals that are sparse in nature, meaning that the signal is periodic and does not change significantly over time. The human body naturally generates many signals that are sparse in nature, such as heart beat, brainwaves, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a prior art sensor network.

FIG. 2 depicts an embodiment of a sensor network utilizing compressed sensing and a cloud.

FIG. 3 depicts an embodiment of a compressed sensing analog-to-digital conversion block.

FIG. 4 a depicts the prior art Nyquist method.

FIG. 4 b depicts the prior art compressed sensing method.

FIG. 5 depicts an embodiment of a sensor network utilizing compressed sensing used with a Body Area Network.

FIG. 6 depicts an embodiment of a sensor network utilizing compressed sensing used with a Body Area Network.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

To solve the issues outlined in the prior art section, a new platform sensor network is shown in FIG. 2. Sensor block 210 shares certain blocks with prior art sensor block 200. Namely, sensor block 210 comprises amplifier 100, post processor 102, transmitter 103, and antenna 104. However, unlike the prior art sensor block 200, sensor block 210 contains compressed sensing analog-to-digital conversion block 150. It is to be understood that other sensor blocks similar to sensor block 210 can be used with the same computing device 300. For brevity's sake, only sensor block 210 is depicted in FIG. 2. Compressed sensing is a known technique in other fields. A seminal paper on compressed sensing is “An Introduction to Compressive Sampling,” Emmanuel J. Candes and Michael B. Wakin, IEEE Signal Processing Magazine, March 2008l , which is incorporated by reference herein.

Sensor block 210 communicates with computing device 300 over network 115. Computing device 300 can communicate with the cloud 400 over network 120. Network 115 and network 120 each can comprise a wireless or hardwired network or a combination of the two. Network 115 preferably is a cellular network, such as a 3G or 4G network, and transmitter 103 is capable of transmitting signals over such a network.

In one embodiment, amplifier 100 is implemented as a switched capacitor amplifier with a chopper or other means of mitigating 1/f noise Amplifier 100 optionally can be coupled to one or more electrodes used to measure electrical data directly from a human patient. Compressed sensing analog-to-digital conversion block 150 can be implemented using a switched capacitor multiplier. Post processor 102 can be implemented as a programmable state machine which can be configurable for various standards and security requirements. Transmitter 103 can be an ultra low power switched capacitor class C amplifier. In this way the whole system can be implemented with a CMOS ASIC and a few external components such as antenna and bio-medical tissue interface.

Additional detail regarding compressed sensing analog-to-digital conversion block 150 is shown in FIG. 3 and FIGS. 4 a and 4 b. FIG. 4 a depicts the traditional Nyquist sampling method, and FIG. 4 b depicts the more recently developed compressed sensing method. By not having to store a lot of data (as is the case in FIG. 4 a and Nyquist sampling), and then discarding it, compressed sensing, as depicted in FIG. 4 b, saves valuable power in the way it performs compression. Compressed sensing is a relatively new phenomenon that uses knowledge of signal sparsity. The compressed sensing front end will require a randomization matrix to mix with the input signal. This will spread the frequency content of the signal and prevent eavesdropping, much like with spread spectrum communication.

By utilizing compressed sensing analog-to-digital conversion block 150, the sensor network of FIGS. 2 and 3 will use substantially less power than the prior art sensor network of FIG. 1. The sampling rate of both the compressed sensing analog-to-digital conversion block 150 and transmitter 103 is reduced by the compression factor when compared to analog-to-digital conversion block 101 and transmitter 103 of sensor block 200. This leads to a direct savings in power. Post processor 102 will also operate on less data in sensor block 210 than in sensor block 200, leading to further power savings. With reference to FIG. 3, compressed sensing analog-to-digital conversion block 150 can utilize a compression rate of 8×16×, which will lead to a similar decrease in power consumption for sensor block 210 compared to prior art sensor block 200.

In another embodiment, to further reduce power, post processor 102 or transmitter 103 can queue the packets of compressed data in memory and then transmit in burst mode instead of in a continual fashion.

The proposed network helps in managing “big data.” Big data consists of 3 components: velocity, volume and value. In the embodiment of FIG. 2, computing device 300 is connected to cloud 400 where the data is extracted in the raw form for processing. In this embodiment, the data is processed by cloud computing device 400 and not computing device 300. Because computing device 300 does not perform the data extraction and processing, it too can be optimized for low power consumption. Using compressed sensing will lower the storage cost for the data by as much as 10×20×.

FIGS. 5 and 6 show an application of the invention to body area networks. The data is transmitted from sensor block 210, sensor block 211, sensor block 212, and any number of other sensor blocks 21 n, using the same functional design of sensor block 210 shown in FIGS. 2 and 3. Here, sensor block 210 comprises EEG (electroencephalography) electrodes 310 for obtaining electrical data from a human patient's scalp, sensor block 211 comprises ECG (electrocardiography) electrodes 311 for obtaining electrical data from a human patient's heart, and sensor block 212 comprises CTG (cardiotocography) electrodes 312 for obtaining electrical data from human patient's uterine contractions and fetal heartbeat. Sensor block 21 n comprises electrodes 31 n, or other physical sensors, for obtaining other medical or biological data from a human patient.

Computing device 300 here is a smart phone. Computing device 300 optionally comprises a software application that enables a user of computing device 300 to view graphical or numerical representations of the data collected by sensor block 210, sensor block 211, and other sensor blocks 21 n. Concurrently, the data will be transmitted to cloud computing device 400 where it can be processed.

References to the present invention herein are not intended to limit the scope of any claim or claim term, but instead merely make reference to one or more features that may be covered by one or more of the claims. Materials, processes and numerical examples described above are exemplary only, and should not be deemed to limit the claims. It should be noted that, as used herein, the terms “over” and “on” both inclusively include “directly on” (no intermediate materials, elements or space disposed there between) and “indirectly on” (intermediate materials, elements or space disposed there between). Likewise, the term “adjacent” includes “directly adjacent” (no intermediate materials, elements or space disposed there between) and “indirectly adjacent” (intermediate materials, elements or space disposed there between). For example, forming an element “over a substrate” can include forming the element directly on the substrate with no intermediate materials/elements there between, as well as forming the element indirectly on the substrate with one or more intermediate materials/elements there between. 

What is claimed is:
 1. A sensor block for collecting data from a human patient, comprising: an amplifier; a compressed sensing analog-to-digital conversion block coupled to the amplifier; a post processor coupled to the compressed sensing analog-to-digital conversion block; a transmitter coupled to the post processor; and an antenna.
 2. The sensor block of claim 1, wherein the compressed sensing analog-to-digital conversion block comprises a random number generator for encrypting data.
 3. The sensor block of claim 1, wherein the compressed sensing analog-to-digital conversion block utilizes a compression factor of 8 or greater.
 4. The sensor block of claim 1, wherein the sensor block comprises electroencephalography electrodes.
 5. The sensor block of claim 1, wherein the sensor block comprises electrocardiography electrodes.
 6. The sensor block of claim 1, wherein the sensor block comprises cardiotocography electrodes.
 7. A body area network for collecting and processing data from a human patient, comprising: a sensor block comprising: an amplifier; a compressed sensing analog-to-digital conversion block coupled to the amplifier; a post processor coupled to the compressed sensing analog-to-digital conversion block; a transmitter coupled to the post processor; and an antenna; a smartphone coupled to the sensor block over a wireless network; and a cloud computing device coupled to the smartphone over a wireless network.
 8. The body area network of claim 7, wherein the compressed sensing analog-to-digital conversion block comprises a random number generator for encrypting data.
 9. The body area network of claim 7, wherein the compressed sensing analog-to-digital conversion block utilizes a compression factor of 8 or greater.
 10. The body area network of claim 7, wherein the sensor block comprises electroencephalography sensors.
 11. The body area network of claim 7, wherein the sensor block comprises electrocardiography sensors.
 12. The body area network of claim 7, wherein the sensor block comprises cardiotocography sensors.
 13. A method of collecting and processing data from a human patient, comprising: obtaining data from the human patient using electrodes; generating compressed data using a compressed sensing analog-to-digital conversion block operating on the data from the human patient; processing the compressed data using a post processor to generate processed data; transmitting the processed data to a smartphone over a wireless network; and transmitting the processed data from the smartphone to a cloud computing device over a wireless network.
 14. The method of claim 13, wherein the data from the human patient comprises electroencephalography data.
 15. The method of claim 13, wherein the data from the human patient comprises electrocardiography data.
 16. The method of claim 13, wherein the data from the human patient comprises cardiotocography data.
 17. The method of claim 13, further comprising: generating graphical representations of the processed data on the smartphone.
 18. The method of claim 17, further comprising: generating numerical representations of the processed data on the smartphone.
 19. The method of claim 13, further comprising: queuing packets of processed data in memory.
 20. The method of claim 19, wherein the step of transmitting the processed data to a smartphone comprises transmitting packets of processed data in burst mode. 